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Microbio Lab 1 pt1
Microbio Lab 1
| Question | Answer |
|---|---|
| In your own words, describe your general goal in the microbiology lab | To develop manipulative, process, and thinking skills. To be able to practice laboratory techniques and skills through repetition |
| Why should you repeat lab tests or perform more than one test to identify microorganisms? | Results are not always reproducible. The bacteria could mutate, resulting in the loss of ability to produce a particular protein or enzyme |
| What is the average generation time of most bacteria? | 30-60 minutes |
| What is the total magnification of the ocular of your laboratory microscopes? | 10X |
| List the three magnifications of the three objectives located on the nosepiece of your microscope | Low-power: 10X/ High-dry: 40X/ Oil immersion: 100X |
| What is the total magnification of the high dry objective? Oil immersion? | 400X// 1000X |
| What part of the microscope moves during focusing? | Fine adjustment |
| What is the function of the iris diaphragm? | Controls the amount of light passing through the specimen |
| Describe the procedure for locating a specimen under low-power | Rotate the low-power objective into viewing position/ Place slide (stained side up)/ secure with clips/ raise stage with course adjustment knob/ look through ocular and adjust until specimen is in focus |
| What is a temporary mount? Why is it used? | Glass slide with a drop of water containing organisms. Contains large number and will be rapidly moving. / Cover mount with a cover slip |
| What is the function of immersion oil? | Used to obtain a greater magnification and to reduce distortion |
| Describe the procedure for applying immersion oil to a slide for observation | First focus with scanner, low-power, high-dry/ rotate high-dry objective and oil immersion halfway to apply a small drop of oil on plate/ Rotate oil immersion obj into place/ Use ONLY fine adjustment for clearer vision |
| Describe the inversion phenomenon? | Reversal of an image projected by a microscope |
| List at least two problems with culturing microbes | Risk of contamination/ Culture fails to grow |
| Nutrient broth vs. Nutrient Agar | NB Contains nutrients required for microbial growth/ NA is solidified NB (Agar has been added) |
| Describe the position of plates of agar when not in use | Plates should remain inverted to prevent contamination/ Do not leave plate exposed to air |
| Why should test tubes always be kept in test-tube racks? | To keep them stable/ to prevent breakage and spread of substance |
| When should a test tube containing a bacterial sample be flamed? | Before and after transferring microbes, to avoid contamination |
| Describe the procedure used to prepare 10 plates of NA pt. 1 | Determine the amount of culture medium needed/ Obtain correct amount of distilled or deionized water using a graduated cylinder transfer water to a beaker |
| Describe the procedure used to prepare 10 plates of NA pt.2 | Calculate the mass (in grams) of dehydrated medium needed for this volume/ Place a piece of filter-paper on the pan of the balance/ zero out scale/ Using a spatula, transfer agar powder to the paper until the scale reaches the correct mass of media |
| Describe the procedure used to prepare 10 plates of NA pt.3 | Transfer media powder to flask/ place a bar magnet in flask along with water and powder medium/ turn heat to high and spin to low/ wait for foamy boil |
| Describe the procedure used to prepare 10 plates of NA pt.4 | Take off of hot plate with heat gloves/ Take magnet out, cover with foil and place in autoclave/ Once cycle finishes, pour NA into plates and allow to cool |
| What type of sterilization is used to disinfect work areas? | Chemical |
| When should you work area be sterilized? | Before and after you work |
| Describe dry sterilization. When is it used? | Hight temps are maintained for long periods of time. It is used for glassware |
| Describe wet sterilization. When is it used? | Uses the autoclave cycle that reaches 121 Celsius under increased pressure of 15 psi. Kills all life forms in 15 minutes/ Used on media, solutions, heat-stable supplies |
| Describe cold sterilization. When is it used? | Organisms are mechanically removed by passing the solutions through a filter of pore size less than the diameter of the organism into a sterile flask/ Used on heat-sensitive solutions, ex. plasma |
| What instrument provides the proper temperature and environment for the growth of microorganisms? | Incubator |
| At what temperature do microbes grow best? | 37 degrees Celsius |
| What is the usual culture duration for microbial cultures? | 24-48 hrs, and no longer than 7 days |
| Describe the procedure for plate disposal | Plates are placed in a plastic bag for autoclaving, to kill all life forms |
| Pathogenic microorganisms will not be used but all organisms should be handled with respect, why? | Basic lab techniques apply to all microbes. Proper technique allows the production of the most pure culture (axenic) and avoid contamination |
Created by:
Clinton Perdue
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